11.4: Congressional Representation
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Learning Objectives
By the end of this section, you will be able to:
- Explain the basics of representation
- Describe the extent to which Congress as a body represents the U.S. population
- Explain the concept of collective representation
- Describe the forces that influence congressional approval ratings
The tension between local and national politics described in the previous section is essentially a struggle between interpretations of representation. Representation is a complex concept. It can mean paying careful attention to the concerns of constituents, understanding that representatives must act as they see fit based on what they feel best for the constituency, or relying on the particular ethnic, racial, or gender diversity of those in office. In this section, we will explore three different models of representation and the concept of descriptive representation. We will look at the way members of Congress navigate the challenging terrain of representation as they serve, and all the many predictable and unpredictable consequences of the decisions they make.
Types of Representation: Looking out for Constituents
By definition and title, senators and House members are representatives. This means they are intended to be drawn from local populations around the country so they can speak for and make decisions for those local populations, their constituents, while serving in their respective legislative houses. That is, representation refers to an elected leader’s looking out for his or her constituents while carrying out the duties of the office. 26
Theoretically, the process of constituents voting regularly and reaching out to their representatives helps these congresspersons better represent them. It is considered a given by some in representative democracies that representatives will seldom ignore the wishes of constituents, especially on salient issues that directly affect the district or state. In reality, the job of representing in Congress is often quite complicated, and elected leaders do not always know where their constituents stand. Nor do constituents always agree on everything. Navigating their sometimes contradictory demands and balancing them with the demands of the party, powerful interest groups, ideological concerns, the legislative body, their own personal beliefs, and the country as a whole can be a complicated and frustrating process for representatives.
Traditionally, representatives have seen their role as that of a delegate, a trustee, or someone attempting to balance the two. A representative who sees him- or herself as a delegate believes he or she is empowered merely to enact the wishes of constituents. Delegates must employ some means to identify the views of their constituents and then vote accordingly. They are not permitted the liberty of employing their own reason and judgment while acting as representatives in Congress. This is the delegate model of representation.
In contrast, a representative who understands their role to be that of a trustee believes he or she is entrusted by the constituents with the power to use good judgment to make decisions on the constituents’ behalf. In the words of the eighteenth-century British philosopher Edmund Burke, who championed the trustee model of representation, “Parliament is not a congress of ambassadors from different and hostile interests . . . [it is rather] a deliberative assembly of one nation, with one interest, that of the whole.” 27 In the modern setting, trustee representatives will look to party consensus, party leadership, powerful interests, the member’s own personal views, and national trends to better identify the voting choices they should make.
Understandably, few if any representatives adhere strictly to one model or the other. Instead, most find themselves attempting to balance the important principles embedded in each. Political scientists call this the politico model of representation. In it, members of Congress act as either trustee or delegate based on rational political calculations about who is best served, the constituency or the nation.
For example, every representative, regardless of party or conservative versus liberal leanings, must remain firm in support of some ideologies and resistant to others. On the political right, an issue that demands support might be gun rights; on the left, it might be a woman’s right to an abortion. For votes related to such issues, representatives will likely pursue a delegate approach. For other issues, especially complex questions the public at large has little patience for, such as subtle economic reforms, representatives will tend to follow a trustee approach. This is not to say their decisions on these issues run contrary to public opinion. Rather, it merely means they are not acutely aware of or cannot adequately measure the extent to which their constituents support or reject the proposals at hand. It could also mean that the issue is not salient to their constituents. Congress works on hundreds of different issues each year, and constituents are likely not aware of the particulars of most of them.
Descriptive Representation in Congress
In some cases, representation can seem to have very little to do with the substantive issues representatives in Congress tend to debate. Instead, proper representation for some is rooted in the racial, ethnic, socioeconomic, gender, and sexual identity of the representatives themselves. This form of representation is called descriptive representation.
At one time, there was relatively little concern about descriptive representation in Congress. A major reason is that until well into the twentieth century, white men of European background constituted an overwhelming majority of the voting population. African Americans were routinely deprived of the opportunity to participate in democracy, and Hispanics and other minority groups were fairly insignificant in number and excluded by the states. While women in many western states could vote sooner, all women were not able to exercise their right to vote nationwide until passage of the Nineteenth Amendment in 1920, and they began to make up more than 5 percent of either chamber only in the 1990s.
Many advances in women’s rights have been the result of women’s greater engagement in politics and representation in the halls of government, especially since the founding of the National Organization for Women in 1966 and the National Women’s Political Caucus (NWPC) in 1971. The NWPC was formed by Bella Abzug (Figure 11.11), Gloria Steinem, Shirley Chisholm, and other leading feminists to encourage women’s participation in political parties, elect women to office, and raise money for their campaigns. For example, Patsy Mink (D-HI) (Figure 11.11), the first Asian American woman elected to Congress, was the coauthor of the Education Amendments Act of 1972, Title IX of which prohibits sex discrimination in education. Mink had been interested in fighting discrimination in education since her youth, when she opposed racial segregation in campus housing while a student at the University of Nebraska. She went to law school after being denied admission to medical school because of her gender. Like Mink, many other women sought and won political office, many with the help of the NWPC. Today, EMILY’s List, a PAC founded in 1985 to help elect pro-choice Democratic women to office, plays a major role in fundraising for female candidates. In the 2018 midterm elections, thirty-four women endorsed by EMILY's List won election to the U.S. House. 28 In 2020, the Republicans took a page from the Democrats' playbook when they made the recruitment and support of quality female candidates a priority and increased the number of Republican women in the House from thirteen to twenty-eight, including ten seats formerly held by Democrats. 29
In the wake of the Civil Rights Movement, African American representatives also began to enter Congress in increasing numbers. In 1971, to better represent their interests, these representatives founded the Congressional Black Caucus (CBC), an organization that grew out of a Democratic select committee formed in 1969. Founding members of the CBC include John Conyers (D-MI), currently the longest-serving member of the House of Representatives, Charles Rangel (D-NY), and Shirley Chisholm, a founder of the NWPC and the first African American woman to be elected to the House of Representatives (Figure 11.12).
In recent decades, Congress has become much more descriptively representative of the United States. The 117th Congress, which began in January 2021 had a historically large percentage of racial and ethnic minorities. African Americans made up the largest percentage, with sixty-two members (including two delegates and two people who would soon resign to serve in the executive branch), while Latinos accounted for fifty-four members (including two delegates and the Resident Commissioner of Puerto Rico), up from thirty just a decade before. 30 Yet, demographically speaking, Congress as a whole is still a long way from where the country is and is composed of largely White wealthy men. For example, although more than half the U.S. population is female, only 25 percent of Congress is. Congress is also overwhelmingly Christian (Figure 11.13).
Representing Constituents
Ethnic, racial, gender, or ideological identity aside, it is a representative’s actions in Congress that ultimately reflect his or her understanding of representation. Congress members’ most important function as lawmakers is writing, supporting, and passing bills. And as representatives of their constituents, they are charged with addressing those constituents’ interests. Historically, this job has included what some have affectionately called “bringing home the bacon” but what many (usually those outside the district in question) call pork-barrel politics. As a term and a practice, pork-barrel politics—federal spending on projects designed to benefit a particular district or set of constituents—has been around since the nineteenth century, when barrels of salt pork were both a sign of wealth and a system of reward. While pork-barrel politics are often deplored during election campaigns, and earmarks—funds appropriated for specific projects—are no longer permitted in Congress (see feature box below), legislative control of local appropriations nevertheless still exists. In more formal language, allocation , or the influencing of the national budget in ways that help the district or state, can mean securing funds for a specific district’s project like an airport, or getting tax breaks for certain types of agriculture or manufacturing.
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Language and Metaphor
The language and metaphors of war and violence are common in politics. Candidates routinely “smell blood in the water,” “battle for delegates,” go “head-to-head,” and “make heads roll.” But references to actual violence aren’t the only metaphorical devices commonly used in politics. Another is mentions of food. Powerful speakers frequently “throw red meat to the crowds”; careful politicians prefer to stick to “meat-and-potato issues”; and representatives are frequently encouraged by their constituents to “bring home the bacon.” And the way members of Congress typically “bring home the bacon” is often described with another agricultural metaphor, the “earmark.”
In ranching, an earmark is a small cut on the ear of a cow or other animal to denote ownership. Similarly, in Congress, an earmark is a mark in a bill that directs some of the bill’s funds to be spent on specific projects or for specific tax exemptions. Since the 1980s, the earmark has become a common vehicle for sending money to various projects around the country. Many a road, hospital, and airport can trace its origins back to a few skillfully drafted earmarks.
Relatively few people outside Congress had ever heard of the term before the 2008 presidential election, when Republican nominee Senator John McCain touted his career-long refusal to use the earmark as a testament to his commitment to reforming spending habits in Washington. 31 McCain’s criticism of the earmark as a form of corruption cast a shadow over a previously common legislative practice. As the country sank into recession and Congress tried to use spending bills to stimulate the economy, the public grew more acutely aware of its earmarking habits. Congresspersons then were eager to distance themselves from the practice. In fact, the use of earmarks to encourage Republicans to help pass health care reform actually made the bill less popular with the public.
In 2011, after Republicans took over the House, they outlawed earmarks. But with deadlocks and stalemates becoming more common, some quiet voices have begun asking for a return to the practice. They argue that Congress works because representatives can satisfy their responsibilities to their constituents by making deals. The earmarks are those deals. By taking them away, Congress has hampered its own ability to “bring home the bacon.”
Are earmarks a vital part of legislating or a corrupt practice that was rightly jettisoned? Pick a cause or industry, and investigate whether any earmarks ever favored it, or research the way earmarks have hurt or helped your state or district, and decide for yourself.
Follow-up activity: Find out where your congressional representative stands on the ban on earmarks and write to support or dissuade them.
Such budgetary allocations aren’t always looked upon favorably by constituents. Consider, for example, the passage of the ACA in 2010. The desire for comprehensive universal health care had been a driving position of the Democrats since at least the 1960s. During the 2008 campaign, that desire was so great among both Democrats and Republicans that both parties put forth plans. When the Democrats took control of Congress and the presidency in 2009, they quickly began putting together their plan. Soon, however, the politics grew complex, and the proposed plan became very contentious for the Republican Party.
Nevertheless, the desire to make good on a decades-old political promise compelled Democrats to do everything in their power to pass something. They offered sympathetic members of the Republican Party valuable budgetary concessions; they attempted to include allocations they hoped the opposition might feel compelled to support; and they drafted the bill in a purposely complex manner to avoid future challenges. These efforts, however, had the opposite effect. The Republican Party’s constituency interpreted the allocations as bribery and the bill as inherently flawed, and felt it should be scrapped entirely. The more Democrats dug in, the more frustrated the Republicans became (Figure 11.14).
The Republican opposition, which took control of the House during the 2010 midterm elections, promised constituents they would repeal the law. Their attempts were complicated, however, by the fact that Democrats still held the Senate and the presidency. Yet, the desire to represent the interests of their constituents compelled Republicans to use another tool at their disposal, the symbolic vote. During the 112th and 113th Congresses, Republicans voted more than sixty times to either repeal or severely limit the reach of the law. They understood these efforts had little to no chance of ever making it to the president’s desk. And if they did, he would certainly have vetoed them. But it was important for these representatives to demonstrate to their constituents that they understood their wishes and were willing to act on them.
Historically, representatives have been able to balance their role as members of a national legislative body with their role as representatives of a smaller community. The Obamacare fight, however, gave a boost to the growing concern that the power structure in Washington divides representatives from the needs of their constituency. 32 This has exerted pressure on representatives to the extent that some now pursue a more straightforward delegate approach to representation. Indeed, following the 2010 election, a handful of Republicans began living in their offices in Washington, convinced that by not establishing a residence in Washington, they would appear closer to their constituents at home. 33
Collective Representation and Congressional Approval
The concept of collective representation describes the relationship between Congress and the United States as a whole. That is, it considers whether the institution itself represents the American people, not just whether a particular member of Congress represents his or her district. Predictably, it is far more difficult for Congress to maintain a level of collective representation than it is for individual members of Congress to represent their own constituents. Not only is Congress a mixture of different ideologies, interests, and party affiliations, but the collective constituency of the United States has an even-greater level of diversity. Nor is it a solution to attempt to match the diversity of opinions and interests in the United States with those in Congress. Indeed, such an attempt would likely make it more difficult for Congress to maintain collective representation. Its rules and procedures require Congress to use flexibility, bargaining, and concessions. Yet, it is this flexibility and these concessions, which many now interpret as corruption, that tend to engender the high public disapproval ratings experienced by Congress.
After many years of deadlocks and bickering on Capitol Hill, the national perception of Congress has tended to run under 20 percent approval in recent years, with large majorities disapproving. Through mid-2021, the Congress, narrowly under Democratic control, was receiving higher approval ratings, above 30 percent. However, congressional approval still lags public approval of the presidency and Supreme Court by a considerable margin. In the two decades following the Watergate scandal in the early 1970s, the national approval rating of Congress hovered between 30 and 40 percent, then trended upward in the 1990s, before trending downward in the twenty-first century. 34
Yet, incumbent reelections have remained largely unaffected. The reason has to do with the remarkable ability of many in the United States to separate their distaste for Congress from their appreciation for their own representative. Paradoxically, this tendency to hate the group but love one’s own representative actually perpetuates the problem of poor congressional approval ratings. The reason is that it blunts voters’ natural desire to replace those in power who are earning such low approval ratings.
As decades of polling indicate, few events push congressional approval ratings above 50 percent. Indeed, when the ratings are graphed, the two noticeable peaks are at 57 percent in 1998 and 84 percent in 2001 (Figure 11.15). In 1998, according to Gallup polling, the rise in approval accompanied a similar rise in other mood measures, including President Bill Clinton’s approval ratings and general satisfaction with the state of the country and the economy. In 2001, approval spiked after the September 11 terrorist attacks and the Bush administration launched the "War on Terror," sending troops first to Afghanistan and later to Iraq. War has the power to bring majorities of voters to view their Congress and president in an overwhelmingly positive way. 35
Nevertheless, all things being equal, citizens tend to rate Congress more highly when things get done and more poorly when things do not get done. For example, during the first half of President Obama’s first term, Congress’s approval rating reached a relative high of about 40 percent. Both houses were dominated by members of the president’s own party, and many people were eager for Congress to take action to end the deep recession and begin to repair the economy. Millions were suffering economically, out of work, or losing their jobs, and the idea that Congress was busy passing large stimulus packages, working on finance reform, and grilling unpopular bank CEOs and financial titans appealed to many. Approval began to fade as the Republican Party slowed the wheels of Congress during the tumultuous debates over Obamacare and reached a low of 9 percent following the federal government shutdown in October 2013.
One of the events that began the approval rating’s downward trend was Congress’s divisive debate over national deficits. A deficit is what results when Congress spends more than it has available. It then conducts additional deficit spending by increasing the national debt. Many modern economists contend that during periods of economic decline, the nation should run deficits, because additional government spending has a stimulative effect that can help restart a sluggish economy. Despite this benefit, voters rarely appreciate deficits. They see Congress as spending wastefully during a time when they themselves are cutting costs to get by.
The disconnect between the common public perception of running a deficit and its legitimate policy goals is frequently exploited for political advantage. For example, while running for the presidency in 2008, Barack Obama slammed the deficit spending of the George W. Bush presidency, saying it was “unpatriotic.” This sentiment echoed complaints Democrats had been issuing for years as a weapon against President Bush’s policies. Following the election of President Obama and the Democratic takeover of the Senate, the concern over deficit spending shifted parties, with Republicans championing a spendthrift policy as a way of resisting Democratic policies.
Link to Learning
Find your representative at the U.S. House website and then explore their website and social media accounts to see whether the issues on which your representative spends time are the ones you think are most appropriate.


4: International Relations Theory
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Theories of International Relations allow us to understand and try to make sense of the world around us through various lenses, each of which represents a different theoretical perspective. In order to consider the field as a whole for beginners it is necessary to simplify IR theory. This chapter does so by situating IR theory on a three-part spectrum of traditional theories, middle-ground theories and critical theories. Examples are used throughout to help bring meaning and perspective to these positions. Readers are also encouraged to consult this book’s companion text, International Relations Theory (2017), which expands greatly on the subject matter of this chapter.
Before we get started, one very important note. You may notice that some of the theories you are introduced to here are referred to by names that also occur in other disciplines. Sometimes this can be confusing as, for example, realism in IR is not the same as realism in art. Similarly, you may hear the word ‘liberal’ being used to describe someone’s personal views, but in IR liberalism means something quite distinct. To avoid any confusion, this note will serve as a caveat that in this chapter we only refer to the theories concerned as they have been developed within the discipline of International Relations.


12: Movement
Paints cannot physically move on our canvas, but artists can paint in a way that gives the illusion or suggestion of movement. This typically involves arranging shapes in a way that leads the viewer from one point to the next in the painting; or using certain techniques with the brush or palette knife to mimic movement.
Perhaps the best example of movement in art (or at least the most famous) is Vincent van Gogh's The Starry Night , featured as the cover image for this chapter, which takes your eyes on a rollercoaster around all the twists and swirls. A similar daytime painting by Van Gogh, seen below, also captures the feeling of movement.
Movement … sounds exciting doesn’t it – like dancing. Dance itself, is an art form entirely based on movement. Visual art uses movement as well, but in a different way. In the painting below, by John Singer Sargent, we see the rhythm of the waves creating the illusion of movement.
Visual movement is the principle of art used to create the impression of action in a work of art. In the painting below, by George Bellows, we see violent movement in the ring as two boxers struggle during a bout. The action is made even more dramatic through the use of strong lighting on the subject (chiaroscuro).
Movement can apply to a single component in a composition, or to the whole composition at once. Visual movement is dependent on the other elements and principles of art . Rhythm, line, color, balance, and space are all examples of elements and principles of art that can play a major role in developing movement in a work of art.
Creating Movement with Rhythm
In the arts, rhythm is most closely associated with music and dance. Musical rhythm involves a beat that is repeated over time. Visual rhythm is created by repeating shapes (a pattern), lines, colors, or any other visual component.
Visual rhythm is everywhere. Rows of windows and columns add rhythm to architecture. Books on a shelf and tiled floors add rhythm to daily life. Each of these examples have something that is repeated. In the painting below, we see rhythm established by the lining up of similar forms and shapes representing cars, people, and buildings.
The repeating element is generally referred to as a motif . To create movement through rhythm, an artwork must have a motif. In the artwork below we see organic shapes repeated in a vertical orientation. Both have the suggestion of movement. The dancers suggest a vibrant dance through the bands of color representing the costumes and the movement of hands, arms and heads in dramatic fashion. The green organic plant-like forms suggest seaweed swaying in ocean swells or other natural forms.
If a motif is variable in size and spacing, then the rhythm is said to be irregular. An irregular rhythm feels natural. Trees growing in a forest have an irregular rhythm. Each tree is unique. Some are thin and some are wide, but all are trees. The arrangement of wild flowers in a garden also create an aesthetically pleasing organic rhythm. The below painting beautifully captures that quality.
Assignment:
Part 1:
Use photography (your own), cut paper, ink drawing, color pencils and/or painting to create an abstract 2-D or representational composition showing movement.
This assignment is “wide open” to allow you to express yourself. Genre explored can be exaggerated forms creating movement and tension, cartoons, series of images showing the passage of time, images indicating natural growth or other images indicating movement. Use your imagination. Always remember that the DESIGN is still the most important consideration.
Take considerable time to closely examine design techniques learned from previous chapters and how you apply them in your composition. The placement of Line, Shape and Color should be an intellectual process that you can defend. Does the Visual Field have a vertical and horizontal grid? Are Line and Shape relating clearly to the Visual Field edge? Are you utilizing the available art tools such as squares, compass and French curves to assist you in the assembly and creation of the composition?
Artistic craftsmanship is becoming more and more critical as the semester continues. Again, are you making progress and improving in this critical area?
Student work by Mariana Nuñez
Student work
Part 2:
On a separate sheet of paper list the design considerations incorporated into Part 1. Be prepared to defend during critique your list relative to your design.


4.3: Accessory Structures of the Skin
By the end of the section, you will be able to:
- Identify the accessory structures of the skin
- Describe the structure and function of hair and nails
- Describe the structure and function of sweat glands and sebaceous glands
Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. These structures embryologically originate from the epidermis and can extend down through the dermis into the hypodermis.
Hair
Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells. Strands of hair originate in an epidermal penetration of the dermis called the hair follicle . The hair shaft is the part of the hair not anchored to the follicle, and much of this is exposed at the skin’s surface. The rest of the hair, which is anchored in the follicle, lies below the surface of the skin and is referred to as the hair root . The hair root ends deep in the dermis at the hair bulb , and includes a layer of mitotically active basal cells called the hair matrix . The hair bulb surrounds the hair papilla , which is made of connective tissue and contains blood capillaries and nerve endings from the dermis (Figure \(\PageIndex{1}\)).
Just as the basal layer of the epidermis forms the layers of epidermis that get pushed to the surface as the dead skin on the surface sheds, the basal cells of the hair bulb divide and push cells outward in the hair root and shaft as the hair grows. The medulla forms the central core of the hair, which is surrounded by the cortex , a layer of compressed, keratinized cells that is covered by an outer layer of very hard, keratinized cells known as the cuticle . These layers are depicted in a longitudinal cross-section of the hair follicle (Figure \(\PageIndex{2}\)), although not all hair has a medullary layer. Hair texture (straight, curly) is determined by the shape and structure of the cortex, and to the extent that it is present, the medulla. The shape and structure of these layers are, in turn, determined by the shape of the hair follicle. Hair growth begins with the production of keratinocytes by the basal cells of the hair bulb. As new cells are deposited at the hair bulb, the hair shaft is pushed through the follicle toward the surface. Keratinization is completed as the cells are pushed to the skin surface to form the shaft of hair that is externally visible. The external hair is completely dead and composed entirely of keratin. For this reason, our hair does not have sensation. Furthermore, you can cut your hair or shave without damaging the hair structure because the cut is superficial. Most chemical hair removers also act superficially; however, electrolysis and yanking both attempt to destroy the hair bulb so hair cannot grow.
The wall of the hair follicle is made of three concentric layers of cells. The cells of the internal root sheath surround the root of the growing hair and extend just up to the hair shaft. They are derived from the basal cells of the hair matrix. The external root sheath , which is an extension of the epidermis, encloses the hair root. It is made of basal cells at the base of the hair root and tends to be more keratinous in the upper regions. The glassy membrane is a thick, clear connective tissue sheath covering the hair root, connecting it to the tissue of the dermis.
Hair serves a variety of functions, including protection, sensory input, thermoregulation, and communication. For example, hair on the head protects the skull from the sun. The hair in the nose and ears, and around the eyes (eyelashes) defends the body by trapping and excluding dust particles that may contain allergens and microbes. Hair of the eyebrows prevents sweat and other particles from dripping into and bothering the eyes. Hair also has a sensory function due to sensory innervation by a hair root plexus surrounding the base of each hair follicle. Hair is extremely sensitive to air movement or other disturbances in the environment, much more so than the skin surface. This feature is also useful for the detection of the presence of insects or other potentially damaging substances on the skin surface. Each hair root is connected to a smooth muscle called the arrector pili that contracts in response to nerve signals from the sympathetic nervous system, making the external hair shaft “stand up.” The primary purpose for this is to trap a layer of air to add insulation. This is visible in humans as goose bumps and even more obvious in animals with a heavier coat than most humans, such as dogs and cats that raise their fur when alarmed.
Hair Growth
Hair grows and is eventually shed and replaced by new hair. This occurs in three phases. The first is the anagen phase, during which cells divide rapidly at the root of the hair, pushing the hair shaft up and out. The length of this phase is measured in years, typically from 2 to 7 years. The catagen phase lasts only 2 to 3 weeks, and marks a transition from the hair follicle’s active growth. Finally, during the telogen phase, the hair follicle is at rest and no new growth occurs. At the end of this phase, which lasts about 2 to 4 months, another anagen phase begins. The basal cells in the hair matrix then produce a new hair follicle, which pushes the old hair out as the growth cycle repeats itself. Hair typically grows at the rate of 0.3 mm per day during the anagen phase. On average, 50 hairs are lost and replaced per day. Hair loss occurs if there is more hair shed than what is replaced and can happen due to hormonal or dietary changes. Hair loss can also result from the aging process, or the influence of hormones.
Hair Color
Similar to the skin, hair gets its color from the pigment melanin, produced by melanocytes in the hair papilla. Different hair color results from differences in the type of melanin, which is genetically determined. As a person ages, the melanin production decreases, and hair tends to lose its color and becomes gray and/or white.
Nails
The nail bed is a specialized structure of the epidermis that is found at the tips of our fingers and toes. The nail body is formed on the nail bed , and protects the tips of our fingers and toes as they are the farthest extremities and the parts of the body that experience the maximum mechanical stress (Figure \(\PageIndex{3}\)). In addition, the nail body forms a back-support for picking up small objects with the fingers. The nail body is composed of densely packed dead keratinocytes. The epidermis in this part of the body has evolved a specialized structure upon which nails can form. The nail body forms at the nail root , which has a matrix of proliferating cells from the stratum basale that enables the nail to grow continuously. The lateral nail fold overlaps the nail on the sides, helping to anchor the nail body. The nail fold that meets the proximal end of the nail body forms the nail cuticle , also called the eponychium . The nail bed is rich in blood vessels, making it appear pink, except at the base, where a thick layer of epithelium over the nail matrix forms a crescent-shaped region called the lunula (the “little moon”). The area beneath the free edge of the nail, furthest from the cuticle, is called the hyponychium . It consists of a thickened layer of stratum corneum.
Sweat Glands
When the body becomes warm, sudoriferous glands produce sweat to cool the body. Sweat glands develop from epidermal projections into the dermis. There are two types of sweat glands, each secreting slightly different products.
An eccrine sweat gland is type of gland that produces a hypotonic sweat for thermoregulation. These glands are found all over the skin’s surface, but are especially abundant on the palms of the hand, the soles of the feet, and the forehead (Figure \(\PageIndex{4}\)). They are coiled glands lying deep in the dermis, with the duct rising up to a pore on the skin surface, where the sweat is released. This type of sweat, released by exocytosis, is hypotonic and composed mostly of water, with some salt, antibodies, traces of metabolic waste, and dermicidin, an antimicrobial peptide. Eccrine glands are a primary component of thermoregulation in humans and thus help to maintain homeostasis.
An apocrine sweat gland is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions. Apocrine sweat glands are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis, with the duct normally emptying into the hair follicle. In addition to water and salts, apocrine sweat includes organic compounds that make the sweat thicker and subject to bacterial decomposition and subsequent smell. The release of this sweat is under both nervous and hormonal control, and plays a role in the poorly understood human pheromone response. Most commercial antiperspirants use an aluminum-based compound as their primary active ingredient to stop sweat. When the antiperspirant enters the sweat gland duct, the aluminum-based compounds precipitate due to a change in pH and form a physical block in the duct, which prevents sweat from coming out of the pore.
Sebaceous Glands
A sebaceous gland is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair. Most sebaceous glands are associated with hair follicles. They generate and excrete sebum , a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable. The fatty acids of sebum also have antibacterial properties, and prevent water loss from the skin in low-humidity environments. The secretion of sebum is stimulated by hormones, many of which do not become active until puberty. Thus, sebaceous glands are relatively inactive during childhood.
Concept Review
Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. Hair is made of dead keratinized cells, and gets its color from melanin pigments. Nails, also made of dead keratinized cells, protect the extremities of our fingers and toes from mechanical damage. Sweat glands and sebaceous glands produce sweat and sebum, respectively. Each of these fluids has a role to play in maintaining homeostasis. Sweat cools the body surface when it gets overheated and helps excrete small amounts of metabolic waste. Sebum acts as a natural moisturizer and keeps the dead, flaky, outer keratin layer healthy.
Review Questions
Q. In response to stimuli from the sympathetic nervous system, the arrector pili ________.
A. are glands on the skin surface
B. can lead to excessive sweating
C. are responsible for goose bumps
D. secrete sebum
- Answer
-
Answer: C
Q. The hair matrix contains ________.
A. the hair follicle
B. the hair shaft
C. the glassy membrane
D. a layer of basal cells
- Answer
-
Answer: D
Q. Eccrine sweat glands ________.
A. are present on hair
B. are present in the skin throughout the body and produce watery sweat
C. produce sebum
D. act as a moisturizer
- Answer
-
Answer: B
Q. Sebaceous glands ________.
A. are a type of sweat gland
B. are associated with hair follicles
C. may function in response to touch
D. release a watery solution of salt and metabolic waste
- Answer
-
Answer: B
Q. Similar to the hair, nails grow continuously throughout our lives. Which of the following is furthest from the nail growth center?
A. nail bed
B. hyponychium
C. nail root
D. eponychium
- Answer
-
Answer: B
Critical Thinking Questions
Q. Explain the differences between eccrine and apocrine sweat glands.
- Answer
-
A. Eccrine sweat glands are all over the body, especially the forehead and palms of the hand. They release a watery sweat, mixed with some metabolic waste and antibodies. Apocrine glands are associated with hair follicles. They are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis. They release a thicker sweat that is often decomposed by bacteria on the skin, resulting in an unpleasant odor.
Q. Describe the structure and composition of nails.
- Answer
-
A. Nails are composed of densely packed dead keratinocytes. They protect the fingers and toes from mechanical stress. The nail body is formed on the nail bed, which is at the nail root. Nail folds, folds of skin that overlap the nail on its side, secure the nail to the body. The crescent-shaped region at the base of the nail is the lunula.
Glossary
- anagen
- active phase of the hair growth cycle
- apocrine sweat gland
- type of sweat gland that is associated with hair follicles in the armpits and genital regions
- arrector pili
- smooth muscle that is activated in response to external stimuli that pull on hair follicles and make the hair “stand up”
- catagen
- transitional phase marking the end of the anagen phase of the hair growth cycle
- cortex
- in hair, the second or middle layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb
- cuticle
- in hair, the outermost layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb
- eccrine sweat gland
- type of sweat gland that is common throughout the skin surface; it produces a hypotonic sweat for thermoregulation
- eponychium
- nail fold that meets the proximal end of the nail body, also called the cuticle
- external root sheath
- outer layer of the hair follicle that is an extension of the epidermis, which encloses the hair root
- glassy membrane
- layer of connective tissue that surrounds the base of the hair follicle, connecting it to the dermis
- hair
- keratinous filament growing out of the epidermis
- hair bulb
- structure at the base of the hair root that surrounds the dermal papilla
- hair follicle
- cavity or sac from which hair originates
- hair matrix
- layer of basal cells from which a strand of hair grows
- hair papilla
- mass of connective tissue, blood capillaries, and nerve endings at the base of the hair follicle
- hair root
- part of hair that is below the epidermis anchored to the follicle
- hair shaft
- part of hair that is above the epidermis but is not anchored to the follicle
- hyponychium
- thickened layer of stratum corneum that lies below the free edge of the nail
- internal root sheath
- innermost layer of keratinocytes in the hair follicle that surround the hair root up to the hair shaft
- lunula
- basal part of the nail body that consists of a crescent-shaped layer of thick epithelium
- medulla
- in hair, the innermost layer of keratinocytes originating from the hair matrix
- nail bed
- layer of epidermis upon which the nail body forms
- nail body
- main keratinous plate that forms the nail
- nail cuticle
- fold of epithelium that extends over the nail bed, also called the eponychium
- nail fold
- fold of epithelium at that extend over the sides of the nail body, holding it in place
- nail root
- part of the nail that is lodged deep in the epidermis from which the nail grows
- sebaceous gland
- type of oil gland found in the dermis all over the body and helps to lubricate and waterproof the skin and hair by secreting sebum
- sebum
- oily substance that is composed of a mixture of lipids that lubricates the skin and hair
- sudoriferous gland
- sweat gland
- telogen
- resting phase of the hair growth cycle initiated with catagen and terminated by the beginning of a new anagen phase of hair growth
Contributors and Attributions
-
OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology


20.5: Cosmic Rays
By the end of this section, you will be able to:
- Define cosmic rays and describe their composition
- Explain why it is hard to study the origin of cosmic rays, and the current leading hypotheses about where they might come from
In addition to gas and dust, a third class of particles, noteworthy for the high speeds with which they travel, is found in interstellar space. Cosmic rays were discovered in 1911 by an Austrian physicist, Victor Hess, who flew simple instruments aboard balloons and showed that high-speed particles arrive at Earth from space (Figure 20.17). The term “cosmic ray” is misleading, implying it might be like a ray of light, but we are stuck with the name. They are definitely particles and have nearly the same composition as ordinary interstellar gas. Their behavior, however, is radically different from the gas we have discussed so far.
The Nature of Cosmic Rays
Cosmic rays are mostly high-speed atomic nuclei and electrons. Speeds equal to 90% of the speed of light are typical. Almost 90% of the cosmic rays are hydrogen nuclei (protons) stripped of their accompanying electron. Helium and heavier nuclei constitute about 9% more. About 1% of cosmic rays have masses equal to the mass of the electron, and 10–20% of these carry positive charge rather than the negative charge that characterizes electrons. A positively charged particle with the mass of an electron is called a positron and is a form of antimatter (we discussed antimatter in The Sun: A Nuclear Powerhouse).
The abundances of various atomic nuclei in cosmic rays mirror the abundances in stars and interstellar gas, with one important exception. The light elements lithium, beryllium, and boron are far more abundant in cosmic rays than in the Sun and stars. These light elements are formed when high-speed, cosmic-ray nuclei of carbon, nitrogen, and oxygen collide with protons in interstellar space and break apart. (By the way, if you, like most readers, have not memorized all the elements and want to see how any of those we mention fit into the sequence of elements, you will find them all listed in Appendix K in order of the number of protons they contain.)
Cosmic rays reach Earth in substantial numbers, and we can determine their properties either by capturing them directly or by observing the reactions that occur when they collide with atoms in our atmosphere. The total energy deposited by cosmic rays in Earth’s atmosphere is only about one-billionth the energy received from the Sun, but it is comparable to the energy received in the form of starlight. Some of the cosmic rays come to Earth from the surface of the Sun, but most come from outside the solar system.
Where Do They Come From?
There is a serious problem in identifying the source of cosmic rays. Since light travels in straight lines, we can tell where it comes from simply by looking. Cosmic rays are charged particles, and their direction of motion can be changed by magnetic fields. The paths of cosmic rays are curved both by magnetic fields in interstellar space and by Earth’s own field. Calculations show that low-energy cosmic rays may spiral many times around Earth before entering the atmosphere where we can detect them. If an airplane circles an airport many times before landing, it is difficult for an observer to determine the direction from which it originated. So, too, after a cosmic ray circles Earth several times, it is impossible to know where its journey began.
There are a few clues, however, about where cosmic rays might be generated. We know, for example, that magnetic fields in interstellar space are strong enough to keep all but the most energetic cosmic rays from escaping the Galaxy. It therefore seems likely that they are produced somewhere inside the Galaxy. The only likely exceptions are those with the very highest energy. Such cosmic rays move so rapidly that they are not significantly influenced by interstellar magnetic fields, and thus, they could escape our Galaxy. By analogy, they could escape other galaxies as well, so some of the highest-energy cosmic rays that we detect may have been created in some distant galaxy. Still, most cosmic rays must have their source inside the Milky Way Galaxy .
We can also estimate how far typical cosmic rays travel before striking Earth. The light elements lithium, beryllium, and boron hold the key. Since these elements are formed when carbon, nitrogen, and oxygen strike interstellar protons, we can calculate how long, on average, cosmic rays must travel through space in order to experience enough collisions to account for the amount of lithium and the other light elements that they contain. It turns out that the required distance is about 30 times around the Galaxy. At speeds near the speed of light, it takes perhaps 3–10 million years for the average cosmic ray to travel this distance. This is only a small fraction of the age of the Galaxy or the universe, so cosmic rays must have been created fairly recently on a cosmic timescale.
The best candidates for a source of cosmic rays are the supernova explosions, which mark the violent deaths of some stars (and which we will discuss in The Death of Stars). The material ejected by the explosion produces a shock wave, which travels through the interstellar medium. Charged particles can become trapped, bouncing back and forth across the front of the shock wave many times. With each pass through the shock, the magnetic fields inside it accelerate the particles more and more. Eventually, they are traveling at close to the speed of light and can escape from the shock to become cosmic rays. Some collapsed stars (including star remnants left over from supernova explosions) may, under the right circumstances, also serve as accelerators of particles. In any case, we again find that the raw material of the Galaxy is enriched by the life cycle of stars. In the next section, we will look at this enrichment process in more detail.
You can watch a brief video about the Calorimetric Electron Telescope (CALET) mission, a cosmic ray detector at the International Space Station. The link takes you to NASA Johnson’s “Space Station Live: Cosmic Ray Detector for ISS.”


2.7: Diet and Weight Control
Who should lose weight?
Health care professionals generally agree that people who have a BMI of 30 or greater can improve their health through weight loss.This is especially true for people with a BMI of 40 or greater, who are considered extremely obese.
Preventing additional weight gain is recommended if you have a BMI between 25 and 29.9, unless you have other risk factors for obesity-related diseases. Obesity experts recommend you try to lose weight if you have two or more of the following:
- Family history of certain chronic diseases. If you have close relatives who have had heart disease or diabetes, you are more likely to develop these problems if you are obese.
- Preexisting medical conditions. High blood pressure, high LDL cholesterol levels, low HDL cholesterol levels, high triglycerides, and high blood glucose are all warning signs of some obesity-associated diseases.
- Large waist circumference. Men who have waist circumferences greater than 40 inches, and women who have waist circumferences greater than 35 inches, are at higher risk of diabetes, dyslipidemia (abnormal amounts of fat in the blood), high blood pressure, and heart disease.
Fortunately, a weight loss of 5 to 10 percent of your initial body weight can do much to improve health by lowering blood pressure and other risk factors for obesity-related diseases. In addition, research shows that a 5- to 7-percent weight loss brought about by moderate diet and exercise can delay or possibly prevent type 2 diabetes in people at high risk for the disease. In a recent study, participants who were considered overweight and had pre-diabetes—a condition in which a person’s blood glucose level is higher than normal, but not high enough to be classified as diabetes—were able to delay or prevent the onset of type 2 diabetes by adopting a low-fat, low-calorie diet and exercising for 30 minutes a day, 5 days a week.
Selecting a Weight Loss Program
Some people lose weight on their own; others like the support of a structured program. Overweight people who are successful at losing weight, and keeping it off, can reduce their risk factors for heart disease. If you decide to join any kind of weight-control program, here are some questions to ask before you join.
-
Does the program provide counseling to help you change your eating activity and personal habits?
The program should teach you how to change permanently those eating habits and lifestyle factors, such as lack of physical activity, that have contributed to weight gain. -
Is the staff made up of a variety of qualified counselors and health professionals such as nutritionists, registered dietitians, doctors, nurses, psychologists, and exercise physiologists?
You need to be evaluated by a physician if you have any health problems, are currently taking any medicine or plan on taking any medicine, or plan to lose more than 15 to 20 pounds. If your weight-control plan uses a very low-calorie diet (a special liquid formula that replaces all food for 1 to 4 months), an exam and followup visits by a doctor also are needed. -
Is training available on how to deal with times when you may feel stressed and slip back to old habits?
The program should provide long-term strategies to deal with weight problems you may have in the future. These strategies might include things like setting up a support system and establishing a physical activity routine. - Is attention paid to keeping the weight off? How long is this phase? Choose a program that teaches skills and techniques to make permanent changes in eating habits and levels of physical activity to prevent weight gain.
-
Are food choices flexible and suitable? Are weight goals set by the client and the health professional?
The program should consider your food likes and dislikes and your lifestyle when your weight-loss goals are planned.
There are other questions you can ask about how well a weight-loss program works. Because many programs don’t gather this information, you may not get answers. But it’s still important to ask them:
- What percentage of people complete the program?
- What is the average weight loss among people who finish the program?
- What percentage of people have problems or side effects? What are they?
- Are there fees or costs for additional items, such as dietary supplements?
Guide to Behavior Change
Your Weight Is Important
Over the past few years it has become clear that weight is an important health issue. Some people who need to lose weight for their health don’t recognize it, while others who don’t need to lose weight want to get thinner for cosmetic reasons. We understand that in some ways your weight is different from, for example, your cholesterol level or your blood pressure, because you can’t see what these are by looking at someone. Many patients have had health care providers who approached their weight in a less-than-sensitive or helpful manner. Some patients may have had health care encounters in which they felt blamed, but not helped. Successful weight management is a long-term challenge.
Weight can affect a person’s self-esteem. Excess weight is highly visible and evokes some powerful reactions, however unfairly, from other people and from the people who carry the excess weight. The amount of weight loss needed to improve your health may be much less than you wish to lose, when you consider how you evaluate your weight. Research has shown that your health can be greatly improved by a loss of 5–10 percent of your starting weight. That doesn’t mean you have to stop there, but it does mean that an initial goal of losing 5–10 percent of your starting weight is both realistic and valuable.
Behaviors That Will Help You Lose Weight and Maintain It
Set the Right Goals
Setting the right goals is an important first step. Most people trying to lose weight focus on just that one goal: weight loss. However, the most productive areas to focus on are the dietary and physical activity changes that will lead to long-term weight change. Successful weight managers are those who select two or three goals at a time that are manageable.
Useful goals should be (1) specific; (2) attainable (doable); and (3) forgiving (less than perfect). “Exercise more” is a great goal, but it’s not specific. “Walk 5 miles every day” is specific and measurable, but is it doable if you’re just starting out? “Walk 30 minutes every day” is more attainable, but what happens if you’re held up at work one day and there’s a thunderstorm during your walking time another day? “Walk 30 minutes, 5 days each week” is specific, doable, and forgiving. In short, a great goal!
Nothing Succeeds Like Success
Shaping is a behavioral technique in which you select a series of short-term goals that get closer and closer to the ultimate goal (e.g., an initial reduction of fat intake from 40 percent of calories to 35 percent of calories, and later to 30 percent). It is based on the concept that “nothing succeeds like success.” Shaping uses two important behavioral principles: (1) consecutive goals that move you ahead in small steps are the best way to reach a distant point; and (2) consecutive rewards keep the overall effort invigorated.
Reward Success (But Not With Food)
An effective reward is something that is desirable, timely, and dependent on meeting your goal. The rewards you choose may be material (e.g., a movie or music download, or a payment toward buying a more costly item) or an act of self-kindness (e.g., an afternoon off from work or just an hour of quiet time away from family). Frequent small rewards, earned for meeting smaller goals, are more effective than bigger rewards that require a long, difficult effort.
Balance Your Food Checkbook
“Self-monitoring” refers to observing and recording some aspect of your behavior, such as calorie intake, servings of fruits and vegetables, amount of physical activity, etc., or an outcome of these behaviors, such as weight. Self-monitoring of a behavior can be used at times when you’re not sure how you’re doing, and at times when you want the behavior to improve. Self-monitoring of a behavior usually moves you closer to the desired direction and can produce “real-time” records for review by you and your health care provider. For example, keeping a record of your physical activity can let you and your provider know quickly how you’re doing. When the record shows that your activity is increasing, you’ll be encouraged to keep it up. Some patients find that specific self-monitoring forms make it easier, while others prefer to use their own recording system.
While you may or may not wish to weigh yourself frequently while losing weight, regular monitoring of your weight will be essential to help you maintain your lower weight. When keeping a record of your weight, a graph may be more informative than a list of your weights. When weighing yourself and keeping a weight graph or table, however, remember that one day’s diet and exercise patterns won’t have a measurable effect on your weight the next day. Today’s weight is not a true measure of how well you followed your program yesterday, because your body’s water weight will change from day to day, and water changes are often the result of things that have nothing to do with your weight-management efforts.
Avoid a Chain Reaction
Stimulus (cue) control involves learning what social or environmental cues seem to encourage undesired eating, and then changing those cues. For example, you may learn from reflection or from self-monitoring records that you’re more likely to overeat while watching television, or whenever treats are on display by the office coffee pot, or when around a certain friend. You might then try to change the situation, such as by separating the association of eating from the cue (don’t eat while watching television), avoiding or eliminating the cue (leave the coffee room immediately after pouring coffee), or changing the circumstances surrounding the cue (plan to meet your friend in a nonfood setting). In general, visible and reachable food items are often cues for unplanned eating.
 It takes 15 or more minutes for your brain to get the message that you’ve been fed. Eating slowly will help you feel satisfied. Eating lots of vegetables and fruits can make you feel fuller. Another trick is to use smaller plates so that moderate portions do not appear too small. Changing your eating schedule, or setting one, can be helpful, especially if you tend to skip, or delay, meals and overeat later.
Find out about Weight Loss Fraud.
- How can you protect yourself?
- What should you keep in mind when buying supplements?
- How do you spot fraud?
Sources
Who should lose weight?: Understanding Adult Obesity, WIN, NIDDK, NIH, win.niddk.nih.gov/publications/understanding.htm
Selecting a Weight Loss Program: Lose Weight Program , NHLBI, NIH, http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/wtl_prog.htm
Guide to Behavior Change: Guide to Behavior Change , NHLBI, NIH, http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/behavior.htm


8.7: Strategic Objectives and Levels of Strategy
- What are strategic objectives, levels of strategy, and a grand strategy? How are they related?
Once a strategic analysis has been completed, the next step in the strategy process is to establish strategic objectives. At this point, the manager has decided why the company exists and how it will try to fulfill its mission. Strategic analysis has provided information about customer preferences, competitors, and the firm’s resources and capabilities. Now it is time to start planning for success.
Strategic objectives
Strategic objectives are the big-picture goals for the company: they describe what the company will do to try to fulfill its mission. Strategic objectives are usually some sort of performance goal—for example, to launch a new product, increase profitability, or grow market share for the company’s product.
Exhibit 8.6 shows what might be some strategic objectives for Disney. To make people happy (Disney’s vision), Disney focuses on entertainment (its mission). Top executives then decide each year what entertainment products the company will offer. Because Disney is a large corporation (more on that shortly), it has a variety of resources available to create entertainment products to offer. For example, they may decide to release three movies this year, as well as build a new theme park and create five new shows for their television network. In reality, the strategic objectives at Disney are much more complex because some of these choices involve long-term efforts (they cannot build a theme park in one year).
Exhibit 8.6 A Possible Strategic Path from Vision to Objective for Disney (Attribution: Copyright Rice University, OpenStax, under CC-BY 4.0 license)
Exhibit 8.6 A Possible Strategic Path from Vision to Objective for Disney (Attribution: Copyright Rice University, OpenStax, under CC-BY 4.0 license)
Levels of Strategies
Once a firm has set its objectives, it then must turn to the question of how it will achieve them. A business-level strategy is the framework a firm uses to organize its activities, and it is developed by the firm’s top managers. Examples of business-level strategies include cost leadership and differentiation. These strategies are pursued by businesses with a single product or a range of products.
For example, imagine that you own a coffee shop.  You have employees, but you are the manager, owner, and all-around decision-maker. While developing your vision and mission statements, you have already made some basic decisions about how your shop will operate. For example, you have chosen to either offer quick, inexpensive coffee (cost leadership) or a full-service coffee experience (differentiation). That decision impacts whether or not you choose premium or discount suppliers, how your shop is decorated, and how many employees you have to offer attention (service) to your customers. A business-level strategy guides a company in how they approach the activities in the value chain. Operations, for example, would focus on efficiency for a cost leader and focus on adding value for a differentiator.
 If you decide that your objective is to grow, for example, you should set a specific target, say, to grow revenue by 10%. Once you set that specific objective, you can exhibit out exactly what business-level actions you will need to take to reach that target.
Even if a business is much larger than a local coffee shop, the strategic objectives pursued by these larger companies are not significantly different in concept. Large companies such as Nike or Apple, which have many different business units, develop strategies at several levels. Each individual business unit (say Nike Basketball) will have a manager who decides the objectives for that unit, just as in the coffee shop example. However, the company as a whole will have a chief executive officer (the top manager for the company) who develops strategy for the entire corporation. Corporate strategy, the broadest level of strategy, is concerned with decisions about growing, maintaining, or shrinking very large companies. At this level, business-level strategy activities, such as an advertising campaign to attract new customers for a single product line, are not going to be enough to significantly impact the company as a whole.
The corporate CEO essentially manages a group of businesses (unless the firm operates as one business unit) and develops strategies to create success for the overall group. Think of the group of businesses as an investment portfolio: investors try to have a diverse set of investments to spread risk and maximize the performance of the overall portfolio. On any given day, an investment that isn’t doing so well should be offset by one that is doing well. Corporate strategy tries to achieve the same thing, and CEOs have to weigh the pros and cons of each business unit and how it is contributing to the success of the overall corporation. For example, a company that has business units that do well in the winter (ski resorts) will try to also have business units that will perform in the summer (swimming pools) to reduce the risk of having periods of low revenue. One tool that corporate strategists use to understand how each of their businesses contributes to the corporation as a whole is the BCG Matrix , illustrated in Exhibit 8.7.
Exhibit 8.7 The BCG Matrix (Attribution: Copyright Rice University, OpenStax, under CC-BY 4.0 license)
The BCG Matrix gives managers a quick picture of which business units are doing well and which are not. The tool has recommendations for businesses in each quadrant—for example, a business in the dog quadrant should be sold or closed. Cash cows provide income to the corporation, and stars provide growth. A CEO is always trying to balance the group of business units throughout the quadrants to maximize overall corporate performance. Note that the BCG Matrix is not applicable for firm’s that operate in one business unit.
To achieve the scale of growth necessary to meet corporate strategic objectives, a CEO must find ways to develop entirely new business units or reach brand-new markets. For example, for Walmart to grow their 2017 revenue by 5%, they would need to add $25 billion in new revenue. That’s more revenue than opening some new stores could generate. CEOs have several ways of growing their corporations, as shown in Table 8.1.
| Grand Strategy | Strategic Objective | Potential Action | |
|---|---|---|---|
| Business-Level Strategy | Growth | Increase business revenue by 25% |
|
| Corporate-Level Strategy | Growth | Increase corporate revenue by 10% |
|
| International Strategy | Growth | Attract 10% overall market share in a new country |
|
Table 8.1 (Attribution: Copyright Rice University, OpenStax, under CC-BY 4.0 license)
In Walmart’s case, for example, growing has meant expanding its online capabilities to better compete with Amazon. They have acquired new companies to support this goal, including Shoebuy, Jet, ModCloth, and Flipkart to reach customers and increase their online product selection, as well as Parcel, to build delivery services (CBInsights, 2018).
International strategy is similar to corporate strategy because it is concerned with the large-scale actions involved in entering a brand-new geographic market. For companies operating internationally, strategic questions focus on how to successfully enter and compete in a foreign market. International strategy can combine with business-level or corporate-level strategies because a growth strategy at either scale can involve entering new markets to reach new customers.
The Grand Strategy
At all three levels, companies choose a grand strategy in response to the first question they should ask themselves: does the firm want to grow, strive for stability, or take a defensive position in the marketplace? Often, the choice of a grand strategy is based on conditions in the business environment because firms generally want to grow unless something (such as a recession) makes that difficult. Note that a grand strategy and a corporate strategy can overlap significantly.
- A growth strategy involves developing plans to increase the size of the firm in terms of revenue, market share, or geographic reach (often a combination of these, as they can overlap significantly). Walmart is implementing a growth strategy with the acquisitions discussed in the corporate strategy section.
- A stability strategy is a strategy for a company to maintain its current income, market share, or geographic reach. A firm usually works to maintain a stable position when the alternative is to lose ground in one of those categories, for example because of competition or economic factors. In today’s business environment, publicly held firms rarely aim solely to maintain the status quo, because shareholders and the stock market reward firm growth.
- Firms pursue defensive strategies in the face of challenges. A company that is struggling may decide to shrink its operations to reduce costs to survive, for example. A company facing strong new competition may have to radically rethink its product offerings or pricing in order not to lose too much market share to the newcomer. A technological innovation may make a company’s products obsolete (or at least less attractive), forcing it to work to catch up to the new technology. Ford made a defensive decision when it recently decided to stop selling sedans in the United States because of slow sales compared with those of trucks and SUVs.
Operationalizing a Grand Strategy
A firm operationalizes its choice of a grand strategy differently at each level of strategy (business, corporate, international). At the business level, a growth strategy means that the manager will have to develop ways to grow the business by developing new products or expanding the customer base for existing products, either at home or abroad. Expanding a corporation can take a wider variety of forms. The CEO can develop new businesses, expand to new countries, acquire or merge with competitors, or perform previously outsourced activities. International expansion can be accomplished by exporting goods to another country or by acquiring a similar firm in another country to establish the company’s presence in that country. In all three of these cases, the grand strategy would be growth, and the strategic objectives could be expressed in terms of revenue growth, profit growth, market share growth, or even share price growth. Table 8.1 outlines how a grand strategy can be used to develop specific company actions.
- What is the difference between strategic objectives and a strategy?
- Describe the three levels of strategy and what a manager developing strategy at each level is concerned with.
- What is a grand strategy, and how does it relate to strategic objectives and the three levels of strategy?
- What are the three grand strategies, and why would firms pursue each of them?


1.7: Introduction to Operating Systems
What you’ll learn to do: determine what operating system you have.
Every computer has an operating system: put simply, this is the system that allows your computer to operate. It is important to know which operating system your computer has because the steps to accomplish various tasks varies between operating systems. Reading directions on how to change the desktop background in Windows 10 may not help you if you are running Windows XP, and those directions will be useless if you are using a Mac. However, nearly all versions of Windows and macOS are capable of doing the same things.
Contributors and Attributions
CC licensed content, Original
- Introduction to Operating Systems. Authored by : Lumen Learning. License : CC BY: Attribution


9.18: Reading- Lahars, Landslides, and Lavaflow
Lahars and Their Effects
Lahar is an Indonesian term that describes a hot or cold mixture of water and rock fragments flowing down the slopes of a volcano and (or) river valleys. When moving, a lahar looks like a mass of wet concrete that carries rock debris ranging in size from clay to boulders more than 10 m in diameter. Lahars vary in size and speed. Small lahars less than a few meters wide and several centimeters deep may flow a few meters per second. Large lahars hundreds of meters wide and tens of meters deep can flow several tens of meters per second–much too fast for people to outrun.
As a lahar rushes downstream from a volcano, its size, speed, and the amount of water and rock debris it carries constantly change. The beginning surge of water and rock debris often erodes rocks and vegetation from the side of a volcano and along the river valley it enters. This initial flow can also incorporate water from melting snow and ice (if present) and the river it overruns. By eroding rock debris and incorporating additional water, lahars can easily grow to more than 10 times their initial size. But as a lahar moves farther away from a volcano, it will eventually begin to lose its heavy load of sediment and decrease in size.
Eruptions may trigger one or more lahars directly by quickly melting snow and ice on a volcano or ejecting water from a crater lake. More often, lahars are formed by intense rainfall during or after an eruption–rainwater can easily erode loose volcanic rock and soil on hillsides and in river valleys. Some of the largest lahars begin as landslides of saturated and hydrothermally altered rock on the flank of a volcano or adjacent hillslopes. Landslides are triggered by eruptions, earthquakes, precipitation, or the unceasing pull of gravity on the volcano.
Lahars almost always occur on or near stratovolcanoes because these volcanoes tend to erupt explosively and their tall, steep cones are either snow covered, topped with a crater lake, constructed of weakly consolidated rock debris that is easily eroded, or internally weakened by hot hydrothermal fluids. Lahars are also common from the snow- and ice-covered shield volcanoes in Iceland where eruptions of fluid basalt lava frequently occur beneath huge glaciers.
The scenarios listed below illustrate most of the mechanisms by which lahars are generated. For convenience, we’ve grouped the mechanisms according to whether a volcano is erupting, has erupted, or is quiet. Each mechanism is illustrated with one or more case studies.
Volcano Landslides and Their Effects
Landslides are large masses of rock and soil that fall, slide, or flow very rapidly under the force of gravity. These mixtures of debris move in a wet or dry state, or both. Landslides commonly originate as massive rockslides or avalanches which disintegrate during movement into fragments ranging in size from small particles to enormous blocks hundreds of meters across. If the moving rock debris is large enough and contains a large content of water and fine material (typically, >3-5 percent of clay-sized particles), the landslide may transform into a lahar and flow downvalley more than 100 km from a volcano!
Volcano landslides range in size from less than 1 km3 to more than 100 km3. The high velocity (>100 km/hr) and great momentum of landslides allows them to run up slopes and to cross valley divides up to several hundred meters high. For example, the landslide at Mount St. Helens on May 18, 1980, had a volume of 2.5 km3, reached speeds of 50-80 m/s (180-288 km/hr), and surged up and over a 400 m tall ridge located about 5 km from the volcano!
Landslides are common on volcanoes because their massive cones (1) typically rise hundreds to thousands of meters above the surrounding terrain; and (2) are often weakened by the very process that created them–the rise and eruption of molten rock. Each time magma moves toward the surface, overlying rocks are shouldered aside as the molten rock makes room for itself, often creating internal shear zones or oversteepening one or more sides of the cone. Magma that remains within the cone releases volcanic gases that partially dissolve in groundwater, resulting in a hot acidic hydrothermal system that weakens rock by altering rock minerals to clay. Furthermore, the tremendous mass of thousands of layers lava and loose fragmented rock debris can lead to internal faults and fault zones that move frequently as the cone “settles” under the downward pull of gravity.
These conditions permit a number of factors to trigger a landslide or to allow part of a volcano’s cone to simply collapse under the influence of gravity:
- intrusion of magma into a volcano
- explosive eruptions (magmatic or phreatic–steam-driven explosions)
- large earthquake directly beneath a volcano or nearby (typically >M5)
- intense rainfall that saturates a volcano or adjacent tephra-covered hillslopes with water, especially before or during a large earthquake.
A landslide typically destroys everything in its path and may generate a variety of related activity. Historically, landslides have caused explosive eruptions, buried river valleys with tens of meters of rock debris, generated lahars, triggered waves and tsunami, and created deep horseshoe-shaped craters.
By removing a large part of a volcano’s cone, a landslide may abruptly decrease pressure on the shallow magmatic and hydrothermal systems, which can generate explosions ranging from a small steam explosion to large steam- and magma-driven directed blasts. A large landslide often buries valleys with tens to hundreds of meters of rock debris, forming a chaotic landscape marked by dozens of small hills and closed depressions. If the deposit is thick enough, it may dam tributary streams to form lakes in the subsequent days to months; the lakes may eventually drain catastrophically and generate lahars and floods downstream.
Landslides also generate some of the largest and most deadly lahars, either by transforming directly into a lahar or, after it stops moving, from dewatering of the deposit. Historically, however, the most deadly volcano landslide occurred in 1792 when sliding debris from Mt. Mayuyama near Unzen Volcano in Japan slammed into the Ariaka Sea and generated a wave on the opposite side that killed nearly 15,000 people.
On a volcano, landslides typically carve deep gashes into its cone or create large horseshoe-shaped craters hundreds of meters deep and more than a kilometer in width.
Volcanic landslides can do the following:
- Trigger volcanic explosions
- Generate lahars that travel far downstream
- Cause waves and tsunamis in a lake or ocean
- Bury river valleys with rock debris
- Dam tributary streams to form lakes
- Create a crater or scar on the volcano
Lava Flows and Their Effects
Lava flows are streams of molten rock that pour or ooze from an erupting vent. Lava is erupted during either nonexplosive activity or explosive lava fountains. Lava flows destroy everything in their path, but most move slowly enough that people can move out of the way. The speed at which lava moves across the ground depends on several factors, including (1) type of lava erupted and its viscosity; (2) steepness of the ground over which it travels; (3) whether the lava flows as a broad sheet, through a confined channel, or down a lava tube; and (4) rate of lava production at the vent.
Fluid basalt flows can extend tens of kilometers from an erupting vent. The leading edges of basalt flows can travel as fast as 10 km/hour on steep slopes but they typically advance less than 1 km/hour on gentle slopes. But when basalt lava flows are confined within a channel or lava tube on a steep slope, the main body of the flow can reach velocities >30 km/hour.
Viscous andesite flows move only a few kilometers per hour and rarely extend more than 8 km from their vents. Viscous dacite and rhyolite flows often form steep-sided mounds called lava domes over an erupting vent. Lava domes often grow by the extrusion of many individual flows >30 m thick over a period of several months or years. Such flows will overlap one another and typically move less than a few meters per hour.
Everything in the path of an advancing lava flow will be knocked over, surrounded, or buried by lava, or ignited by the extremely hot temperature of lava. When lava erupts beneath a glacier or flows over snow and ice, meltwater from the ice and snow can result in far-reaching lahars. If lava enters a body of water or water enters a lava tube, the water may boil violently and cause an explosive shower of molten spatter over a wide area. Methane gas, produced as lava buries vegetation, can migrate in subsurface voids and explode when heated. Thick viscous lava flows, especially those that build a dome, can collapse to form fast-moving pyroclastic flows.
Deaths caused directly by lava flows are uncommon because most move slowly enough that people can move out the way easily and flows usually don’t travel far from the vent. Death and injury can result when onlookers approach an advancing lava flow too closely or their retreat is cut off by other flows. Deaths attributed to lava flows are often due to related causes, such as explosions when lava interacts with water, the collapse of an active lava delta, asphyxiation due to accompanying toxic gases, pyroclastic flows from a collapsing dome, and lahars from meltwater.
Other natural phenomena such as hurricanes, tornadoes, tsunami, fires, and earthquakes often destroy buildings, agricultural crops, and homes, but the owner(s) can usually rebuild or repair structures and their businesses in the same location. Lava flows, however, can bury homes and agricultural land under tens of meters of hardened black rock; landmarks and property lines become obscured by a vast, new hummocky landscape. People are rarely able to use land buried by lava flows or sell it for more than a small fraction of its previous worth.
Because lava flows can completely block roads and highways that may serve as the only evacuation route for people threatened by an advancing flow, it is vital for communities that could be inundated with lava to develop emergency-response plans.
One of the chief threats of lava flows to property owners is that the flows may burn buildings and homes even if the flow doesn’t reach the structure. This house caught fire from the intense heat of an advancing `a`a flow (note red glow of flow left of the house).
Basalt has the highest temperature of any lava, typically between about 1170-1100°C (~2140-2000°F). The other lava types (andesite, dacite, and rhyolite) form cooler flows with temperatures between about 1000-800°C (~1800-1500°F); some flows can still move slowly at temperatures as low as about 600°C (~1100°F).
Lava melts snow and ice to form jökulhlaups and lahars. By this time, the area of subsidence had grown to about 9 km long and 2-3 km wide. The eruption continued for about another 10 days, and meltwater from the glacier flowed into the Grímsvötn caldera. On October 1, water level in the caldera’s subglacial lake was about 1410 m; by October 16, the water level had risen to 1504 m, an increase of 94 m! According to scientists monitoring the activity, lava erupting from the fissure was piled up on the ground beneath the glacier, “forming a mountain ridge which in places is expected to be 200 m high.”
On October 16, scientists stated that the meltwater, which had been accumulating under the ice shelf in the Grímsvötn caldera lake, could begin draining at any time to trigger a jökulhlaup (glacial outburst flood). On November 5 the expected jökulhlaup began.
Collapsing lava flows trigger pyroclastic flows. The fast-moving pyroclastic flow was caused by the collapse of a thick lava flow that was extruding from the summit area and oozing down the volcano’s steep upper cone. When the lava flow collapsed, the hot lava broke apart into fragments ranging in size from boulders to tiny ash particles and swept down the volcano under the influence of gravity to form the pyroclastic flow; the flow reached a maximum distance of 4.5 km from the summit.
Contributors and Attributions
- Types of Volcano Hazards. Provided by : USGS. Located at : http://volcanoes.usgs.gov/hazards/ . License : Public Domain: No Known Copyright


36.12: Vision - Light
- Describe the characteristics of light
Light
As with auditory stimuli, light travels in waves. While the compression waves that compose sound must travel in a medium (consisting of a gas, a liquid, or a solid), light is composed of electromagnetic waves and needs no medium. Light can, in fact, travel in a vacuum. The behavior of light can be described in terms of the behavior of waves and the behavior of the fundamental unit of light, the photon: a packet of electromagnetic radiation. A glance at the electromagnetic spectrum shows that visible light for humans is just a small slice of the entire spectrum, which includes radiation that we cannot see as light because it is below the frequency of visible red light and above the frequency of visible violet light.
Certain variables are important when discussing perception of light. A wavelength (which varies inversely with frequency) manifests itself as color. Light at the red end of the visible spectrum has longer wavelengths (and is lower frequency), while light at the violet end has shorter wavelengths (and is higher frequency). The wavelength of light is expressed in nanometers (nm); one nanometer is one billionth of a meter. Humans perceive light that ranges between approximately 380 nm and 740 nm. However, some other animals can detect wavelengths outside of the human range. For example, bees see near-ultraviolet light in order to locate nectar guides on flowers. Some non-avian reptiles sense infrared light (such as heat that prey gives off).
Wave amplitude is perceived as luminous intensity or brightness. The standard unit of intensity of light is the candela, which is approximately the luminous intensity of one common candle.
Light waves travel 299,792 km per second in a vacuum and somewhat slower in various media such as air and water. Those waves arrive at the eye as long (red), medium (green), and short (blue) waves. The term “white light” is light that is perceived as white by the human eye. This effect is produced by light that stimulates the color receptors in the human eye equally. The apparent color of an object is actually the color (or colors) the object reflects. Thus a red object reflects the red wavelengths in mixed (white) light and absorbs all other wavelengths of light.
Key Points
- Light is composed of electromagnetic waves that can travel without a medium, unlike sound.
- The behavior of light can be seen in the behavior of waves and photons, the basic unit of light.
- A wavelength (which varies inversely with frequency ) manifests itself as color, while wave amplitude is perceived as luminous intensity or brightness; it is measured by the standard unit of a candela.
- Humans can see light that ranges between 380 nm and 740 nm, but cannot see light that is below the frequency of visible red light or above the frequency of visible violet light.
- Light at the red end of the visible spectrum has long wavelengths (and is lower frequency), while light at the violet end has short wavelengths (and is higher frequency).
- Light waves enter the eye as long (red), medium (green), and short (blue) waves; the color of an object is the color the object reflects.
Key Terms
- photon : the quantum of light and other electromagnetic energy, regarded as a discrete particle having zero rest mass, no electric charge, and an indefinitely long lifetime
- nanometer : one billionth of a meter; used to express wavelength of light
- electromagnetic spectrum : the entire range of wavelengths of all known radiations consisting of oscillating electric and magnetic fields, including gamma rays, visible light, infrared, radio waves, and X-rays
- wavelength : the length of a single cycle of a wave, as measured by the distance between one peak or trough of a wave and the next; it corresponds to the velocity of the wave divided by its frequency


7: Rational Numbers Last updated Save as PDF Page ID 35089 Illustrative Mathematics OpenUp Resources Section 36: Negative Numbers and Absolute Value 36.1: Positive and Negative Numbers 36.2: Points on the Number Line 36.3: Comparing Positive and Negative Numbers 36.4: Ordering Rational Numbers 36.5: Using Negative Numbers to Make Sense of Contexts 36.6: Absolute Value of Numbers 36.7: Comparing Numbers and Distance from Zero Section 37: Inequalities 37.1: Writing and Graphing Inequalities 37.2: Solutions of Inequalities 37.3: Interpreting Inequalities Section 38: The Coordinate Plane 38.1: Points on the Coordinate Plane 38.2: Constructing the Coordinate Plane 38.3: Interpreting Points on a Coordinate Plane 38.4: Distances on a Coordinate Plane 38.5: Shapes on the Coordinate Plane Section 39: Common Factors and Common Multiples 39.1: Common Factors 39.2: Common Multiples 39.3: Using Common Multiples and Common Factors Section 40: Let's Put it to Work 40.1: Drawing on the Coordinate Plane